<template>
  <div class="goods-image">
    <!-- 大图容器 -->
    <div class="large" v-show="show" :style="[{backgroundImage:`url(${images[currIndex]})`},lagePosition]"></div>
    <!-- 中途 -->
    <div class="middle" ref="target">
      <img :src="images[currIndex]" alt="">
      <!-- 遮罩层 -->
      <div class="layer" v-show="show" :style="layerPosition"></div>
    </div>
    <ul class="small">
      <li v-for="(img,i) in images" :key="img" :class="{active:i===currIndex}">
        <img @mouseenter="currIndex=i" :src="img" alt="">
      </li>
    </ul>
  </div>
</template>
<script>
import { reactive, ref, watch } from 'vue'
import { useMouseInElement } from '@vueuse/core'
export default {
  name: 'GoodsImage',
  props: {
    images: {
      type: Array,
      default: () => []
    }
  },
  setup (props) {
    const currIndex = ref(0)
    // 1:是否显示遮罩层和大图
    const show = ref(false)
    // 2:遮罩坐标
    const layerPosition = reactive({
      left: 0,
      top: 0
    })
    // 3:大图定位
    const lagePosition = reactive({
      backgroundPositionX: 0,
      backgroundPositionY: 0
    })
    // 4：基于useMouseInElement得到基于元素左上角坐标和是否离开元素数据
    const target = ref(null)
    const { elementX, elementY, isOutside } = useMouseInElement(target)
    // console.log(elementX, elementY, isOutside)
    // const showLayer = () => {
    //   layerPosition.left = elementX
    //   layerPosition.top = elementY
    // }
    watch([elementX, elementY, isOutside], () => {
      // console.log(elementX.value)
      show.value = !isOutside.value
      // if (isOutside === false) {
      //   layerPosition.left = elementX.value + 'px'
      //   layerPosition.top = elementY.value + 'px'
      // }
      // 边界值判定 x少于100 不动  100-300 动 大于400 为200
      const position = { x: 0, y: 0 }
      if (elementX.value < 100) position.x = 0
      else if (elementX.value > 300) position.x = 200
      else position.x = elementX.value - 100
      // 边界值 y 判定
      if (elementY.value < 100) position.y = 0
      else if (elementY.value > 300) position.y = 200
      else position.y = elementY.value - 100
      // 给样式赋值
      layerPosition.left = position.x + 'px'
      layerPosition.top = position.y + 'px'
      // 大图背景图
      lagePosition.backgroundPositionX = -2 * position.x + 'px'
      lagePosition.backgroundPositionY = -2 * position.y + 'px'
    })
    return { currIndex, show, layerPosition, lagePosition, target }
  }
}
</script>
<style scoped lang="less">
@import '../../../assets/styles/variable.less';
.goods-image {
  width: 480px;
  height: 400px;
  position: relative;
  display: flex;
  .middle {
    width: 400px;
    height: 400px;
    background: #f5f5f5;
     position: relative;
    cursor: move;
    .layer {
      width: 200px;
      height: 200px;
      background: rgba(0,0,0,.2);
      left: 0;
      top: 0;
      position: absolute;
    }
  }
  .small {
    width: 80px;
    li {
      width: 68px;
      height: 68px;
      margin-left: 12px;
      margin-bottom: 15px;
      cursor: pointer;
      &:hover,&.active {
        border: 2px solid @c;
      }
    }
  }
  z-index: 500;
.large {
  position: absolute;
  top: 0;
  left: 412px;
  width: 400px;
  height: 400px;
  box-shadow: 0 0 10px rgba(0,0,0,0.1);
  background-repeat: no-repeat;
  background-size: 800px 800px;
  background-color: #f8f8f8;
}
}
</style>
